Application of stem cells to developmental modeling and cell-based therapy for neuromuscular and musculoskeletal disorders
Our current research focuses on developing stem cell technology for use in treating and modeling neuromuscular diseases. We have engaged in basic and translational studies using human neural progenitor cells, mesenchymal stem cells, and pluripotent stem cells to develop therapeutic strategies for neuromuscular diseases.
In neuromuscular diseases, impaired muscle function may result from pathology in the muscle, nerves innervating the muscle, or the neuromuscular connections. Because most neuromuscular diseases are terminal with few treatment options and no known cures, discovery of new treatments is an urgent demand. The research in my laboratory has been directed towards optimizing applications of stem cells for treatment of neuromuscular diseases, with a primary focus on amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig’s disease), a progressive, neurodegenerative disease in which motor neurons of the spinal cord and brain degenerate, causing paralysis and death due to respiratory failure.
1. New derivation of skeletal muscle stem cells for cell-based therapy and disease modeling.
Stem cell-based therapy is a promising approach to recover skeletal muscle function. Skeletal muscle progenitor/stem cells, also called myogenic progenitors, can differentiate into skeletal muscles and contribute to muscle regeneration. In recent years, various methods have been reported to propagate human myogenic progenitors from pluripotent cell resources and to differentiate these progenitors into skeletal muscle cell lineage as myoblasts or myotubes. Unfortunately, these protocols require manipulations such as cell sorting and over-expression of myogenic genes that limit clinical application, making it difficult to isolate human myogenic progenitors in sufficient quality and quantity for clinical testing. Our group recently reported a unique protocol for the derivation of myogenic progenitors directly (i.e. without genetic modification) from human pluripotent resources using free-floating spherical cultures. Importantly, our method can produce myogenic progenitors from human induced-pluripotent stem cells (iPSCs) generated from both healthy donors and patients with neuromuscular disorders such as ALS, spinal muscular atrophy, muscular dystrophy and Pompe disease (glycogen storage disease type II).
2. Using stem cell technologies to treat and understand neuromuscular diseases.
Our laboratory has engaged in basic and translational studies using human neural progenitor cells, mesenchymal stem cells, and pluripotent stem cells to develop therapeutic strategies to treat ALS. Although most ALS research has been focused on mechanisms of motor neuron cell death, degeneration is also observed in skeletal muscle, particularly the neuromuscular junction (NMJ). Indeed, NMJ degeneration is observed in the early stages of ALS and throughout disease progression. Despite its importance, NMJ pathology has received relatively little attention, possibly because motor neurons survive for prolonged periods without NMJ connections. Effective treatment of ALS will not be possible unless motor neurons survive and their attachments to muscles are preserved.
ALS is an ideal disease target for novel gene and cell therapy approaches as it is both incurable and terminal. Neuroprotective trophic/growth factors promote motor neuron survival and are excellent candidates for gene therapy in both familial and sporadic forms of ALS. Our approach is to use stem cells to deliver neuroprotective trophic/growth factors to the NMJ in the skeletal muscles. We demonstrated the feasibility of this approach in a rat model of familial ALS (SOD1G93A transgenic), where this treatment protected motor neurons by preventing the “dying back” of these cells from the muscle. We recently extended these experiments using human mesenchymal stem cells (hMSCs) to deliver trophic factors postulated to have a role in ALS pathogenesis individually or in combination to NMJ. We used the hMSCs as “Trojan horses” to deliver key trophic factors, including glial cell line-derived neurotrophic factor (GDNF) and vascular endothelial growth factor (VEGF). We reported that combined ex vivo delivery of GDNF and VEGF could extend survival and protect neuromuscular connections and motor neurons in ALS model rats. These pre-clinical data represent a novel and powerful treatment strategy for ALS.
3. Exploring novel techniques for non-invasive imaging of human stem cells.
My research team has also developed a new imaging approach for monitoring the survival and migration of engrafted stem cells. In current preclinical research and clinical trials, the inability to monitor the survival and migration of grafted cells in the brain and other peripheral tissues is a major roadblock for therapy development. Through interdisciplinary collaboration with other faculty members in medical bioengineering and physics, we recently completed a proof-of-concept study for imaging human stem cells with magnetic resonance imaging (MRI) and positron emission tomography (PET) using divalent metal transporter 1 (DMT1), a membrane transporter of manganese and other divalent metals. Our initial studies indicate that this approach holds promise for dual-modality MRI/PET tracking of grafted stem cells in the central nervous system and prompts further investigation into the clinical applicability of this technique.